Some conventional ultrasonic transducer devices, such as the devices described in U.S. Pat. 5,744,898 and U.S. Pat. 8,596,140 B2, tend to be rigid and large in size. These devices are not suited to be adopted as an implantable or ingestible device for non-invasive imaging applications. In some recently improved ultrasound diagnostic imaging devices, such as the devices described in U.S. Patent Application 2014/0276079 A1, a tube/wire is required along with the ultrasound transducers to be inserted into a patient. These devices are also unsuitable to be adopted as an implantable or ingestible device for non-invasive imaging applications. Some other ultrasonic transducer devices, such as the devices described in US Patent Application 2011/0130658 A1 and U.S. Pat. No. 8,647,328 B2, are concerned with using the devices, but fail to address the apparatuses and methods for making such devices small with a plurality of flexible ultrasonic transducers such that these components may be packaged into a sensor device for implantable or ingestible or other non-invasive applications. Therefore, there is a need for a flexible piezoelectric micromechanical ultrasonic transducer array that may be adopted as an implantable or ingestible or other non-invasive applications, and methods for manufacturing the same.